| Juniperus rigida is an important species of water and soil conservation and landscaping in China, and is also the mainly Mongolian and Tibetan medicine. Its essential oil has important health and medical effects. At present, the research on the chemical composition and antioxidant activity of the essential oils and methanol extracts of J. rigida have not been reported. In view of the stems and needles of J. rigida resources has obvious advantages, in order to fully and reasonably use J. rigida resources, the study analyzed the chemical composition and antioxidant activity of J. rigida essential oils and methanol extracts. This can provide theoretical basis for efficient utilization of J. rigida resources. The experimental results are as follows:1.The steam distillation method and supercritical carbon dioxide method were used to study the optimum extraction technology of J. rigida essential oils. The results indicated that the supercritical carbon dioxide extraction is a high efficiency and quality method. The response surface method was used to optimize the supercritical carbon dioxide extraction, The result showed that under pressure 18 MPa, temperature 40°C,time 120 min, the yield of stems essential oil was 2.5%, the needles and berries are 0.8% and 1.0%, respectively.2.The GC-MS was used to analyze chemical composition and content of J. rigida essential oils. Results showed the J. rigida stems essential oils have the most components which is 94, the needles and berries were 62 and 76, respectively. But only 21, 17 and 14 compounds were identified from stems, needles and berries essential oils. In detail, 8 common identified compounds of three parts essential oils were linalool, 2-undecanone, bornyl acetate, α-terpineol acetate, caryophyllene, caryophyllene oxide, germacrene D and α-caryophyllene. the contents of esters(21.23%) and ketones(13.73%) were highest in stems, and the sesquiterpenes(52.99%) content was highest in needles. The major chemical composition were caryophyllene, caryophyllene oxide, germacrene D and α-caryophyllene.However,the mainly chemical composition of berries were α-pinene(20.8%) and β-myrcene(27.4%).3.The methanol was used to extract J. rigida, the study showed that the needles extracts exhibited the highest total phenolic content(19.43 ± 0.85 mmol equiv. GAE/100 g), followed by stems(15.07 ± 0.25 mmol equiv. GAE/100 g). While stems extracts presented the highest total flavonoids content(0.33 ± 0.02 mmol equiv. QUE/100g), followed by needles(0.28 ± 0.01 mmol equiv. QUE/100g) and berries(0.26 ± 0.01 mmol equiv. QUE/100g).4.The phenolic profiles of J. rigida stems, needles and berries were analyzed by RP-HPLC. The results showed that only 10 compounds were determined in needles and stems extracts, 6 in berries. The 10 chemical composition were chlorogenic acid, catechin, cumaric acid, rutin, hyperoside, ellagic acid, podophyllotoxin, amentoflavone, formononetin and galangal, respectively. The total contents of identified compounds varied significantly different among three parts extracts. The podophyllotoxin toxin content of he stems and needles is highest, they are 36.09 ~+ 0.02mg/g and 131.26 ~+ 0.25mg/g, respectively. Also needles have higher content of chlorogenic acid, catechin, these substances content in berries are low. However, the coumaric acid content(10.53 ~+ 0.01mg/g) is the highest in berries.5.Three methods(DPPH, ABTS and FRAP) were used to evaluate antioxidant activities of J. rigida essential oils. The stems essential oil showed the highest capacity to scavenge the DPPH radical and ABTS radical cation, with the values of IC50(4.24 ± 0.17 mg/m L) and 40.29 ± 0.34μmol Trolox/g, respectively, followed by berries and needles essential oils. The needles essential oil exhibited powerful antioxidant activity in FRAP assay, with a highest value of 362.90 ± 9.23μmol Trolox/g. The berries essential oil showed the lowest antioxidant ability in both ABTS and FRAP assay, with the value of 30.31 ± 0.22 μmol Trolox/g and 276.56 ± 5.77 μmol Trolox/g, respectively. The Needles extracts always showed the highest antioxidant activity in three methods, with the values of DPPH(0.20 ± 1.11mg/ML), ABTS value(31.23 ± 0.13 μmol equiv.Trolox/g) and FRAP value(479.57 ± 6.78 μmol equiv Trolox/g), respectively, followed by stems, with the value of DPPH(0.25 ± 4.71mg/ML), ABTS value(29.88 ± 0.17 μmol equiv.Trolox/g) and FRAP value(351.49± 7.15μmol equiv. Trolox/g), However, the berries extracts significantly showed the lowest antioxidant activity in three methods, with the value of DPPH(43 ± 2.57mg/ML), ABTS value(26.56 ± 0.12 μmol equiv.Trolox/g) and FRAP value(170.72 ± 0.87 μmol equiv. Trolox/g), respectively. |
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